/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;
using Lucene.Net.Analysis.Tokenattributes;
using Token = Lucene.Net.Analysis.Token;
using TokenFilter = Lucene.Net.Analysis.TokenFilter;
using TokenStream = Lucene.Net.Analysis.TokenStream;

namespace Lucene.Net.Analysis.Standard
{
    
    /// <summary>Normalizes tokens extracted with <see cref="StandardTokenizer" />. </summary>
    
    public sealed class StandardFilter:TokenFilter
    {
        
        
        /// <summary>Construct filtering <i>in</i>. </summary>
        public StandardFilter(TokenStream in_Renamed):base(in_Renamed)
        {
            termAtt = AddAttribute<ITermAttribute>();
            typeAtt = AddAttribute<ITypeAttribute>();
        }
        
        private static readonly System.String APOSTROPHE_TYPE;
        private static readonly System.String ACRONYM_TYPE;
        
        // this filters uses attribute type
        private ITypeAttribute typeAtt;
        private ITermAttribute termAtt;
        
        /// <summary>Returns the next token in the stream, or null at EOS.
        /// <p/>Removes <tt>'s</tt> from the end of words.
        /// <p/>Removes dots from acronyms.
        /// </summary>
        public override bool IncrementToken()
        {
            if (!input.IncrementToken())
            {
                return false;
            }
            
            char[] buffer = termAtt.TermBuffer();
            int bufferLength = termAtt.TermLength();
            System.String type = typeAtt.Type;
            
            if ((System.Object) type == (System.Object) APOSTROPHE_TYPE && bufferLength >= 2 && buffer[bufferLength - 2] == '\'' && (buffer[bufferLength - 1] == 's' || buffer[bufferLength - 1] == 'S'))
            {
                // Strip last 2 characters off
                termAtt.SetTermLength(bufferLength - 2);
            }
            else if ((System.Object) type == (System.Object) ACRONYM_TYPE)
            {
                // remove dots
                int upto = 0;
                for (int i = 0; i < bufferLength; i++)
                {
                    char c = buffer[i];
                    if (c != '.')
                        buffer[upto++] = c;
                }
                termAtt.SetTermLength(upto);
            }
            
            return true;
        }
        static StandardFilter()
        {
            APOSTROPHE_TYPE = StandardTokenizerImpl.TOKEN_TYPES[StandardTokenizerImpl.APOSTROPHE];
            ACRONYM_TYPE = StandardTokenizerImpl.TOKEN_TYPES[StandardTokenizerImpl.ACRONYM];
        }
    }
}